3.14 Chromosomes

Recall that the nucleus of a cell contains chromosomes in which genes are located

Chromosomes - Genetic information within a cell in the nucleus

1. Chromosome composed of molecule called DNA
- takes shape of double helix

Sections of DNA are called genes
- 1 chromosome can have thousands of genes

Source: http://www.elmhurst.edu/~chm/vchembook/images/580dna.gif

Each gene carries information for construction of protein
Protein gives characteristic associated with gene (e.g. blood group)

DNA (Gene) -> Protein -> Characteristic

2. Different organisms have different numbers of chromosomes
e.g. Cat 38, Chicken 78, Chimp 42, Human 46 (chromosomes per cell)

3. Homologous pairs - genes operating in pairs

Source: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiV4AMLxhPmVPzgztkcFYq64mZVeEWsFfljGLIf9-JLwnV4FMg2qdOsCaT0W_B8O5gbU-9SiNKN2sO0WE8C7l_w6E0cWfAdjnK-PZM1ETUsqhyphenhyphenPcKbY4ExnSmUPVS-a2A7xwH02TqQn2g-i/s400/female+karyogram.jpg

Homologous nature is based on length of chromosomes

Location of gene - gene loci
Same gene loci on homologous pair - same gene

-> 2 versions of each gene for one characteristic
-> Versions are called alleles

http://www.monteweston.com/Biology/Bio/joalleles.gif